User Manual

Enterasys X-Pedition User Reference Manual 279

Protocol Independent Multicast (PIM)

Introduction

Protocol Independent Multicast, PIM, is a multicast routing protocol used to dynamically build a

distribution tree used to forward multicast data on a network. Although group members are at the

“leaves” of the tree, the multicast data transmission source is generally at the root. PIM utilizes

existing unicast routes to perform reverse path forwarding (RPF) checks—essentially a route

lookup on the source—and the routing engine returns the best interface, regardless of how the

routing table is constructed. In this sense, PIM is independent of any routing protocol—PIM can

perform RPF checks using OSPF routes, RIP routes, static routes, or a combination of route types.

Note: See Interoperability on page 310 for restrictions associated with the PIM protocol.

The PIM specifications define several modes or methods by which a PIM router can build the

distribution tree. The mode described in this document is sparse mode (also referred to as PIM-

SM). Sparse Mode utilizes only those routers that need to be included in forwarding multicast data.

Sparse mode routers use bandwidth more efficiently than other modes, but can require more

processing time when working with large numbers of streams.

Features common to all modes include:

1. Using IGMP to propagate group membership information.

! Enable IGMP interfaces.

igmp enable interface 10.135.89.10

igmp enable interface 172.1.1.10

igmp enable interface 207.135.122.11

igmp enable interface 207.135.89.64

! Set IGMP Query Interval

igmp set queryinterval 30

! Enable DVMRP

dvmrp enable interface 10.135.89.10

dvmrp enable interface 172.1.1.10

dvmrp enable interface 207.135.122.11

dvmrp enable interface 207.135.89.64

dvmrp enable interface 10.40.1.10

! Set DVMRP parameters

dvmrp set interface 172.1.1.10 neighbor-timeout 200

! Start DVMRP

dvmrp start